The movement of certain electrically-operated valves, such as certain fuel injectors, comprises a needle that is reciprocated axially within the interior of the valve's body in response to electrical energization and de-energization of an electro-mechanical actuator to thereby selectively open and close a flow path through the valve. Fuel injectors typically contain a solenoid assembly that includes an electromagnetic coil which, when energized, is operative to effect axial movement of an armature.
The state of the art contains a substantial number of patents relating to fuel injector solenoid designs. Typically, a solenoid valve comprises an armature movable between a first and second position for causing a needle valve to contact and separate from a valve seat. The basic solenoid design includes a coil, a stationary ferromagnetic pole, and the movable ferromagnetic armature. The armature is kept separated from the pole by a force such as gravity, spring, or pressure.
Manufacturers of gasoline engines specify in the product engineering specifications the static and dynamic flow rates of a fuel injector. This specification has applied limits typically of +/-3.2% for static flow and +/-3% for dynamic flow. In the manufacturing process, fuel injectors are tested 100% for these characteristics and those falling outside these limits are discarded. Those inside the limits fit a normal statistical distribution typically displayed as a histogram.
When the injector is assembled into an engine the performance of the injector may be from different ends of the statistical distribution. Although still within the overall specification, this can create variables in emissions of the vehicle. This mixture of rich and lean injectors directly affects the emissions.
As governmental standards have become tighter over the years, manufacturers continue to tighten the variability in static and dynamic flows. Industry goals today are in the range of +/-11/2% for a given population. Tighter tolerances require the internal absorption of higher scrap levels, that ultimately shows itself in product cost.
It is seen then that it would be desirable to have a method for providing to a vehicle computer the exact technical data associated with any given fuel injector.